This invention relates to method and apparatus for running tubing in a continuous mode in subsea wells whose wellheads are located on or near the ocean floor or wells located on land.
In the maintenance and servicing of subsea wells several systems have been used. Tools have been developed which involve the erection of a riser pipe on the well. Recently flexible pipe and systems have been developed. See U.S. Pat. Nos. 4,702,320 and 4,730,677.
One well-known system for servicing wells on land has involved the use of coiled tubing, which is forced into a well by a tubing injector. This equipment makes possible the injection of fluid and the use of a well tool on the tubing. See U.S. Pat. No. 4,612,984. Tubing injectors have also been used in the same manner on offshore platforms where the wellhead is located on the platform adjacent the surface of the water and the injector is located on the platform.
Each of these prior art systems has its advantages and disadvantages. Both systems prior applications are not used to drill a well. This is an economic disadvantage, drilling systems are very expensive to purchase, operate and maintain. Also the daily running cost of most floating drilling platforms is very high. Using two systems on the same drilling platform involves the changing of one system to another system which costs time and consequently is an economic disadvantage.
The normal drilling process uses fixed lengths of drill pipe such as range III (45 feet) or range II (30 feet) lengths. Drilling a well involves drilling a length of drill pipe disconnection of the top drive, hoisting the top drive, connection of a new length of drill pipe and drilling the well. Handling the drill pipe on the drill floor is dangerous and a lot of accidents happen of with fatal consequences. When the drilling is completed fixed lengths of casing are lowered into the bore hole using the same method as is being used during drilling. Assembling the desired total lengths of casing using fixed lengths of casing tubulars takes a long time. Connecting the tubulars is equally dangerous compared to the handling of drill pipe. Another disadvantage is that the connection failures between the casing are a main reason for problems occurring during the placement of the casing. This is especially the case when expandable casing is used. It has long been needed to have a drilling method and a method for lowering casing which does not involve separate lengths of tubulars being connected to each other.
An object of the invention is to provide multipurpose reeled tubing assembly, which can run at higher casing running speeds, of a factor of 3 to 5 times faster than conventional running speeds.
Another object of the invention is to eliminate having to use connections with casing prior to running the casing in the riser.
An object of the invention is to increase safety on a rig by eliminating the need for manned operation for making up the casing connection on the drill floor deck, so that safety on the rig is improved. No loose tubulars are on the rig with this process.
During drilling a well a critical parameter is controlling the well at all costs a blow out is to be prevented. Apart from safety issues ultimate well productivity depends strongly on the damage the formation sustained during drilling. Using separate lengths of drill pipe and/or casing requires a discontinue mud flow. Precise control of the mud pressure is not possible. It is highly desired to have a method that can continuously control the well pressure with high accuracy during the drilling and casing installing process.
An object of the invention is to provide a method for flowing fluids into the casing at the same time the casing is run into the riser using a continuous flow process.
Another object of this invention is to provide a simple, relatively inexpensive apparatus and method of installing casing, tubing, telemetrics, cabling and survey cabling through the risers into subsea wells.
During the drilling process there is continuously the need for measuring the properties of the ground where the drilling takes place to determine the optimal well trajectory. Using drilling systems according to prior art some vital measurements could only take place after removal of the drill bit. This involves pulling the complete length of drill pipe which can take considerable time. During the installation of casing no measurements can be made. Also specialized equipment is used which must be installed for each measuring job requiring the mud flow to be stopped. This takes valuable time and is often the reason of formation damage. The possibility to take measurements on a continuous basis while maintaining full well control has long been needed.
An object of the invention is to install into the casing telemetrics and survey equipment for a bore hole in a continuous flow process, so that continuous measurement of the well can occur without a break in the measuring or analysis process.
A know problem during the use of expandable casing is the lowering of the expandable casing in the well bore. In most cases several trips down hole are needed to place expandable casing. This is undesirable due to the time loss and the decreased well control.
An object of the invention is to develop equipment so that when using expandable casing so that two tubulars can be run simultaneously, one inside the other at the same time avoiding the need for additional trips.
An object of the invention is to be able to run two casing lines simultaneously in a continuous flow process.
Another object is to provide for using a reeled assembly to install tubing through subsea risers into subsea wells in a continuous flow manner.
Another object is to provide for using a moveable continuous method for inserting a plurality of tubing or casings through risers into subsea wells simultaneously.
Other objects features and advantages of this invention will be apparent from the drawings, specification and claims.
In the drawings, wherein like numerals indicate like parts and wherein an illustrative embodiment of this invention is shown: